Symptoms and causes

Symptoms

The main symptom of infertility is not getting pregnant. There may be no other obvious symptoms. Sometimes, an infertile woman may have irregular or absent menstrual periods. Rarely, an infertile man may have some signs of hormonal problems, such as changes in hair growth or sexual function.

Most couples will eventually conceive, with or without treatment.

When to see a doctor

You probably don't need to see a doctor about infertility unless you have been trying regularly to conceive for at least one year. Talk with your doctor earlier, however, if you're a woman and:

You're age 35 to 40 and have been trying to conceive for six months or longer

You're over age 40

You menstruate irregularly or not at all

Your periods are very painful

You have known fertility problems

You've been diagnosed with endometriosis or pelvic inflammatory disease

You've had multiple miscarriages

You've undergone treatment for cancer

Talk with your doctor if you're a man and:

You have a low sperm count or other problems with sperm

You have a history of testicular, prostate or sexual problems

You've undergone treatment for cancer

You have testicles that are small in size or swelling in the scrotum known as a varicocele

Causes

Ovulation is the release of an egg from one of the ovaries. It often happens about midway through the menstrual cycle, although the exact timing may vary.

In preparation for ovulation, the lining of the uterus, or endometrium, thickens.

The pituitary gland in the brain stimulates one of the ovaries to release an egg.

The wall of the ovarian follicle ruptures at the surface of the ovary. The egg is released.

Finger-like structures called fimbriae sweep the egg into the neighboring fallopian tube.

The egg travels through the fallopian tube, propelled in part by contractions in the fallopian tube walls.

Here in the fallopian tube, the egg may be fertilized by a sperm.

If the egg is fertilized, the egg and sperm unite to form a one-celled entity called a zygote.

As the zygote travels down the fallopian tube toward the uterus, it begins dividing rapidly to form a cluster of cells resembling a tiny raspberry.

When the zygote reaches the uterus, it implants in the lining of the uterus and pregnancy begins.

If the egg isn't fertilized, it's simply reabsorbed by the body — perhaps before it even reaches the uterus. About two weeks later, the lining of the uterus sheds through the vagina. This is known as menstruation.

Male reproductive system

Male reproductive system

The male reproductive system makes, stores and moves sperm. The testicles produce sperm. Fluid from the seminal vesicles and prostate gland combines with sperm to make semen. The penis ejaculates semen during sexual intercourse.

Fertilization and implantation

Fertilization and implantation

During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine wall — a process called implantation.

Female reproductive system

Female reproductive system

The ovaries, fallopian tubes, uterus, cervix and vagina (vaginal canal) make up the female reproductive system.

All of the steps during ovulation and fertilization need to happen correctly in order to get pregnant. Sometimes the issues that cause infertility in couples are present at birth, and sometimes they develop later in life.

Infertility causes can affect one or both partners. In general:

In about one-third of cases, there is an issue with the male.

In about one-third of cases, there is an issue with the female.

In the remaining cases, there are issues with both the male and female, or no cause can be identified.

Causes of male infertility

These may include:

Abnormal sperm production or function due to undescended testicles, genetic defects, health problems such as diabetes or infections such as chlamydia, gonorrhea, mumps or HIV. Enlarged veins in the testes (varicocele) can also affect the quality of sperm.

Problems with the delivery of sperm due to sexual problems, such as premature ejaculation; certain genetic diseases, such as cystic fibrosis; structural problems, such as a blockage in the testicle; or damage or injury to the reproductive organs.

Overexposure to certain environmental factors, such as pesticides and other chemicals, and radiation. Cigarette smoking, alcohol, marijuana or taking certain medications, such as select antibiotics, antihypertensives, anabolic steroids or others, can also affect fertility. Frequent exposure to heat, such as in saunas or hot tubs, can raise the core body temperature and may affect sperm production.

Damage related to cancer and its treatment, including radiation or chemotherapy. Treatment for cancer can impair sperm production, sometimes severely.

Causes of female infertility

Causes of female infertility may include:

Ovulation disorders, which affect the release of eggs from the ovaries. These include hormonal disorders such as polycystic ovary syndrome. Hyperprolactinemia, a condition in which you have too much prolactin — the hormone that stimulates breast milk production — may also interfere with ovulation. Either too much thyroid hormone (hyperthyroidism) or too little (hypothyroidism) can affect the menstrual cycle or cause infertility. Other underlying causes may include excessive exercise, eating disorders, injury or tumors.

Uterine or cervical abnormalities, including abnormalities with the opening of the cervix, polyps in the uterus or the shape of the uterus. Noncancerous (benign) tumors in the uterine wall (uterine fibroids) may rarely cause infertility by blocking the fallopian tubes. More often, fibroids interfere with implantation of the fertilized egg.

Fallopian tube damage or blockage, often caused by inflammation of the fallopian tube (salpingitis). This can result from pelvic inflammatory disease, which is usually caused by a sexually transmitted infection, endometriosis or adhesions.

Endometriosis, which occurs when endometrial tissue grows outside of the uterus, may affect the function of the ovaries, uterus and fallopian tubes.

Primary ovarian insufficiency (early menopause), when the ovaries stop working and menstruation ends before age 40. Although the cause is often unknown, certain factors are associated with early menopause, including immune system diseases, certain genetic conditions such as Turner syndrome or carriers of Fragile X syndrome, radiation or chemotherapy treatment, and smoking.

Other conditions. Medical conditions associated with delayed puberty or the absence of menstruation (amenorrhea), such as celiac disease, poorly controlled diabetes and some autoimmune diseases such as lupus, can affect a woman's fertility. Genetic abnormalities also can make conception and pregnancy less likely.

Risk factors

Many of the risk factors for both male and female infertility are the same. They include:

Age. A woman's fertility gradually declines with age, especially in her mid-30s, and it drops rapidly after age 37. Infertility in older women may be due to the number and quality of eggs, or to health problems that affect fertility. Men over age 40 may be less fertile than younger men are and may have higher rates of certain medical conditions in offspring, such as psychiatric disorders or certain cancers.

Tobacco use. Smoking tobacco or marijuana by either partner reduces the likelihood of pregnancy. Smoking also reduces the possible benefit of fertility treatment. Miscarriages are more frequent in women who smoke. Smoking can increase the risk of erectile dysfunction and a low sperm count in men.

Alcohol use. For women, there's no safe level of alcohol use during conception or pregnancy. Avoid alcohol if you're planning to become pregnant. Alcohol use increases the risk of birth defects, and may contribute to infertility. For men, heavy alcohol use can decrease sperm count and motility.

Being overweight. Among American women, an inactive lifestyle and being overweight may increase the risk of infertility. A man's sperm count may also be affected if he is overweight.

Being underweight. Women at risk of fertility problems include those with eating disorders, such as anorexia or bulimia, and women who follow a very low calorie or restrictive diet.

Exercise issues. Insufficient exercise contributes to obesity, which increases the risk of infertility. Less often, ovulation problems may be associated with frequent strenuous, intense exercise in women who are not overweight.

Infertility: An overview — A guide for patients. American Society for Reproductive Medicine. http://www.asrm.org/uploadedFiles/ASRM_Content/Resources/Patient_Resources/Fact_Sheets_and_Info_Booklets/infertility_overview.pdf. Accessed May 23, 2016.

Infertility FAQs. Centers for Disease Control and Prevention. http://www.cdc.gov/reproductivehealth/Infertility. Accessed May 23, 2016.

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